There are numerous situations where maintaining continuous tactical military communications is a mission critical requirement. Interruptions in communications can cause confusion, tactical disadvantages and a potential loss of life. Achieving continuous communications capability in the military is made more difficult by the fact that our armed forces often use numerous different types of communications platforms employing different and distinct frequencies and antennas, such as the AN/PSC-5, EPLRS, SATCOM radios and future Joint Tactical Radio System (“JTRS”) terminals.
The difficulties caused by a multiplicity of frequencies and communications devices are exacerbated by the additional complexities caused by operating such different communications devices at a single location or in confined areas. Furthermore, the large number of different communications devices, each with its own unique operating frequency and energy polarization schemes have also spawned a corresponding number of unique antenna systems designed for each specific military radio. Similar situations may also occur in commercial environments such as shipping, transportation and finance where continuous communications are needed amidst multiple communications systems. Multiband communications could become more reliable with a simplified system that permits the user to use a single multiband communications platform with a group of different antennas organized with an autonomous antenna switching apparatus into a single and simplified communications system.
Current military use of the 225–400 MHz spectrum provides a cogent example of the long-felt need for such a simplified system. Most military users of the 225–400 MHz band have adopted vertically polarized energy by convention. However, a small portion of the 225–400 MHz band dedicated to satellite communications requires circular, not vertical, polarization. Adopting the unique conventions for SATCOM signal polarization allows for less interference between satellite and terrestrial VHF communications systems. Prior art passive RF selection devices are unable to determine the precise boundaries of the satellite sub-band and are therefore incapable of selecting the proper antenna.
Thus there has been a long-felt need for communications equipment that permits users to connect a single multiband communications platform to several different antennas and automatically switch between the antennas without suffering from the dangers, disadvantages, shortcomings and limitations of complex and costly equipment and interrupted communications from prior art passive RF selection arrangements. Prior art passive radio frequency selectors are considered deficient because their unintended emissions are losses that can also generate increased RFI/EMI concerns on platforms fitted with multiple antennas.
In order to satisfy this long-felt need for connecting a multiband communications platform to multiple antennas, the present invention provides an automatic antenna-switching apparatus which allows the military and commercial user to connect a single multiband communications platform to a group of antennas with different frequencies by detecting the actual RF energy input and automatically switching to the desired antenna in the group of antennas, without suffering from the problems, shortcomings, disadvantages and limitations of prior art passive selection devices. The present invention provides an automatic antenna-switching apparatus that detects an RF energy input representing the user's selected frequency and makes a logical decision through embedded software to select the properly polarized and matched antenna for the intended radio band. In accordance with the present invention, the automatic antenna-switching apparatus could be provided with either fixed output antenna port selections, or re-programmable selection points to adapt to additional or future bandwidth and antenna requirements. The types of military radios where this apparatus could be used include: the AN/PSC-5, AN/PRC-117, AN/PRC-113, URC-200 and the JTRS system. In commercial communications, the automatic antenna-switching apparatus could be employed in communications centers and in developing mobile communications centers designed to bridge communications systems between military, public service and Homeland Defense missions or applications. This invention's automatic antenna-switching device permits the commercial and military user to employ multiple communications platforms, automatically and autonomously switch from one antenna to another and maintain communications without suffering from the problems, shortcomings, disadvantages and limitations of interrupted service through changes in radio transceivers, or manual selection of antenna systems.